A methanol synthesis process is a very important basic process in chemical industries, and the high efficiency on the methanol synthesis process has been constantly demanded from the viewpoint of saving of energy and economic efficiency.
In conventionally known methanol synthesis processes, a synthetic gas (a mixed gas of CO and H2) is used as a main raw material (containing a small amount of CO2) and a three-component type catalyst such as Cu/ZnO/Al2O3 catalyst (present industrial catalyst, for example Non-patent document 1) and Cu/ZnO/SiO2 catalyst (Patent document 1) is known as its catalyst.
In a conventional methanol synthesis technique using a synthetic gas as a raw material, it is known that the catalyst is stable for a period of several years. In the methanol synthesis using CO2 and H2 as raw materials related to the field of the present invention, the same activity stability of the catalyst has been also desired now but it is difficult to say that the activity stability is sufficient.
Meanwhile, from studies on reuse and recycling of carbon resources in order to decrease GHG (green house effect gas) and on global environment problems, there is increasing interest in a process of methanol synthesis by using CO2 and H2 as main raw materials recently in place of the conventional processes of using a synthetic gas as a main material.
In the methanol synthesis from a raw material gas having a high CO2 content, a catalyst is demanded to have a higher activity than that used in the methanol synthesis from the above synthetic gas for the sake of thermodynamic equilibrium in the reaction and reaction inhibiting effect of water generated together with methanol (Non-patent document 2). Moreover, in the methanol synthesis from a raw material gas having a high CO2 content, the lowering of the catalyst activity, which will be caused by water generated as a by-product together with methanol, is significantly large as compared with the methanol synthesis from a synthetic gas. On this account, the catalyst having a higher durability is demanded as compared with the catalyst used in the methanol synthesis from the synthetic gas. This is considered that the three-component catalyst, which is used in the methanol synthesis from the synthetic gas, does not have sufficient catalyst performance.
Under the circumstances, a copper type multi-component catalyst comprising additional components, such as copper/zinc oxide/aluminum oxide/zirconium oxide, or copper/zinc oxide/aluminum oxide/zirconium oxide/gallium oxide has been developed (for example, Patent documents 2 and 3).
Furthermore, a catalyst having high activity prepared by adding colloidal silica or a water solved silica in an amount of 0.3 to 0.9 wt % as silica and calcination at a temperature of 480 to 690° C. has been developed (Patent document 4).
The present applicant discloses preferable methods of producing these copper type catalysts (Patent documents 5, 6 and 7).